Recurrent Selection for Improved Germination under Water Stress in Russian Dandelion

Russian dandelion [Taraxacum kok-saghyz (TKS)] is a promising candidate for introducing natural rubber production into North America. Seeds normally germinate in a humid microenvironment, such as the thatch layer of a lawn or under a canopy of grass; however, 5% to 15% establishment is often observed on bare soil, presumably due to water stress. Phenotypic selection and half-sib family recurrent selection were conducted for three cycles to improve germination in vitro, under low osmotic potential (Psi(s)), using a polyethylene glycol (PEG) solution. Populations were then tested for establishment on bare soil in the greenhouse and field. Germination under water stress in vitro increased from 5.8% for the cycle 0 (C-0) population to 40.8% and 47.8% for the C-3-phenotypic and C-3-half-sib family populations, respectively. Soil establishment in the greenhouse and field was improved up to two-and 4-fold, respectively, compared with the C-0, in two of four greenhouse experiments and three of eight field experiments. Overall, recurrent selection for germination under water stress in vitro has potential to improve establishment in the field and can be incorporated into current breeding programs to support the overall goal of creating cultivars with high-rubber yield.